DESCRIPTION (Applicant's Description) The most exciting current research in hematopoiesis involves stem cell isolation, characterization, and clinical application, and the molecular physiology of the hematopoietic hormones. Hematopoietic hormones, their receptors, receptor antagonists, and soluble receptors play a crucial role in host defense, and their use in clinical therapy has become one of the most important biologic and clinical topics of the last two decades. Important recent advances include the isolation of thrombopoietin and the discovery and application of new hematopoietic hormones and host defense modulatotors. Our understanding of stem cell physiology is still rudimentary but the hematopoietic stem cell plays a central role in new and creative therapies for neoplastic disease as well as for gene therapy of genetic and certain acquired disorders. The characterization of hemopoietin-signaling pathways in normal and neoplastic cells and the definition of new targets for therapeutic intervention are critical issues. The goal of the conference will be to address the major questions outlined above regarding normal and neoplastic hematopoiesis and host defense. The overall aim is to synthesize the specialized information and define the state of the art in the field. The program will bring together world experts with an assigned agenda and establish an interactive environment for established scientists, graduate students, and postdoctoral fellows.